Code converter and error detector



May 24, 1949. J. A. SPENCER ErAL CODE CONVERTER AND ERROR DETECTOR 5Sheets-Sheet 1 File'd Oct. 24, 1946 May 24, 1949. .Jr AysPENcl-:R E-rALCODE CONVERTER AND ERROR DETECTOR 5 Sheets-Sheet 2 Filed oct. 24, 1946May 24 1949- J. A. SPENCER mm. 2,471,126

CODE CONVERTER N) ERROR DETECTOR 5 Sheets-Sheet 3 Filed oct. 24', 194eMay 24, 1949. l J. A. SPENCER ETAL 2,471,126

coDE CONVERTER AND ERROR DETECTOR Filed'oct. 24, 1946 'ssheets-sheet 4Farbf@ MRy24,1949f j J..A.SPENER HAL 2,471,126

conE CONVERTER AND ERROR DETEcToR I `Filed octr 24.,` 194e @gaats-sheet5 "Wg m Patented May 24, 1949 2,4 7 1,126 CODE CON VERTER AND .ERRORDETECTOR James A.- Spencer, 'Teaneck, N. J., and Lewis A. Thomas,Brooklyn, N. Y., assgnors to Radio .Corporation lof America, acorporation of Dela- Ware Application October 24, 1946, Serial No.705,314

6 Claims. l

This invention relates to telegraph systems and more particularly to atelegraph system invwhich a perforated tape passing through a tapetransmitter actuates a relay translator and distributor, effectingconversion from one standard cod-e to another.

In telegraph systems, messages are frequently received over circuitsemploying one'type voi signalling code and retransmitted over circuitsusing a diiferent code. A number of devices designed to performautomatically the function of translating from one code to anotherhavebeen developed, types of which are exemplified in Spencer PatentsNo. 2,228,417, granted February 18, 1941, and 2,232,082, granted January14, 1941.

Where the transferal from one code to another is used at terminalstations at which the incoming-signals are received by radio, thesignals are peculiarly subject t0 distortion because of fading andinterference. These distortions Amay give rise to erroneous signalsbeing perforated in the tape. It is desirable that some means be devisedto cause a special code group to be perforated upon the reception oferroneous signals. Such a device is disclosed in ASpencer Patent2,231,397, granted February 1l, 1941. Any system for converting from onecode to another should, for maximum eiciency, be capable of retainingduring conversion, the protection gained by detecting and indicatingfaults existing in the received code signal combinations to beretransmitted.

Accordingly, it is an object of this invention to provide an improvedmeans for converting from one code signal system to another.

It is a further object of the invention to detect multilations existingin the received signals and to automatically insert in the convertedcode transmission, signals for causing the receiving printer t0 record aspeoic symbol indicating the occurrence of errors in the received code.

More specifically it is an object of this invention to provide animproved telegraph code signal converter readily adaptable forconverting a multiple element printer code to a multiple element printercode having a fewer number of elements.

Briefly, in accordance with the invention, re ceived signals are fed toa tape transmitter and utilized to actuate a translator and an error detector. Normal signals are then fed through a translator to relays whichestablish converted signals. Upon the reception of an abnormal signal,paths are established through the trans lator to relays which establisha, special converted code signal indicative of the fact that the signalwas'rec'eived in error. The converted'sig nals are then conveyed to adistributor and retransmitted.

The above and other objects and advantages of the invention will becomeapparent upon aconsideration of the following 4detailed description whentaken in conjunction Withfthe accompanying drawings representingschematicallyan em' bodiment of the invention and in which- Fig. 1represents, in block diagramgthebasic elements of the embodiment of theinvention chosen for purposes of illustration,

Fig. 2 represents schematically the circuits 'oi the invention,

Fig. 3 represents schematically the circuits of the tape transmitter andthe translator,

Fig. 4 represents schematically the circuits 'of the converter,

Fig. 5 represents schematically the connections between the conve-rterand the vdistributor and the clearing relay circuit, and

Fig. 6 represents schematicallythe circuits `of the error detector andthe distributor.

From a consideration of the drawings it will be apparent that Fig. 3 hasbeen arranged to go to the left and as a continuation of Fig. 6;"Fi'g. 4arranged to go above Fig. 3 andas a'cont'inuation thereof; and Fig. 5arranged to go toftherl'ght of Fig. 4 and as a continuation thereof asWel] as above and as a continuation of Fig. 6. Throughout the 'drawingslike elements vwill be designated by like reference numerals.

For the purpose of simplifying the description of the operation of theinvention, it will be assumed that it is desired to convert seven unituniform length code signals having 3 mark and 4 space elements to liveunit uniform length code signals having permutated mark elements. Thisassumption is'to be made with the understanding that the invention isnot limited thereto, since it will be apparent that the .benefits of theinvention may be achieved in systems used for conversion of other codes.

Referring to Fig. 1 it will be seen that there has been provided inputmeans IU including -a source of signals to be converted. The signals arethen conducted to an error inserter 12:1and thence to a-translator I4.From the translator I4 the signals are fed to a converter 16 -and thenceto a distributor I8. The distributor II8 functions to deliver theconverted signals tothe output means 2li and also to control certainfunctions of the error inserter l2 and the'input means I0.

The general circuit connections of the invention will be describedprimarily with respect to Fig. 2. It will be seen that there has beenprovided a standard tape transmitter 22 having, in the assumed system,seven pairs of contacts 24. One side of each pair of contacts 24 isconnected by line 2t through contacts 28 operated by cam 30 and thenceto ground. The purpose and functioning or' cam 30 will be describedlater. The other contact of each pair of contacts 24 is connected, withthe exception of the contact corresponding to the last element of theinput code signal, to the translator relays 32, 34, 36, 38, 40, and 42,respectively. At the point of connection of the translator relays andtheir cor* responding Contact among contacts 24 are connected parallelimpedance devices 44, 45, 48, 50, 52, and 54, respectively. The otherterminals of the translator relays are connected through line resistors56, 58, S0, 02, 04, and 6, respectively, to a local source of supply 68.The excepted contact of contacts 24 is connected directly to lineresistor 'I9 and to an impedance device 12 similar to thoseaforementioned. Line resistor l is connected to the local power supply08. Im pedance device 'i2 is connected in parallel with theaforementioned impedance devices. The tape advancing solenoid i4 of tapetransmitter 22 has one terminal connected to ground and the other toline 70. The common line '|8 of parallel impedance devices 44, 4S, 4S,50, 52, 54, and l2 leads to the serially connected windings S0, 02 and84, respectively, of the error-detecting relays and thence to a localsource of operating voltage 85. The winding of error-detecting relay 80is adjusted to operate on a current equal to that owing through one oithe parallel impedance devices such as 50; the winding of relay 82 isadjusted to operate on the current flowing through a predeterminednumber of such impedance devices, in the assumed case, three, and relay84 is adjusted to operate on the current ow through more than thepredetermined number of such impedance devices, in the as- Sumed case,four or more.

The translator relays are equipped with pileups 88, only certain ofwhich are shown, which establish separate output paths for eachdifferent incoming signal such as those indicated for the letter EL U,Q, and L The output circuits are tied together to form the cable 90 andfed to the converter relays, only two of which, relay 92 and relay 94,are shown. It will be noted that relays 92 and 94 each carry a pair ofoperating windings, 95 and 98, and |00 and |02, respectively, and thatcertain of the output circuits from the translator pileups 88 passthrough only one of such windings while others pass through the secondwindings of both coils. The windings of the remaining converter relaysare similarly connected. Winding 96 of relay 92 has one terminalconnected to the proper output lead from cable 90 and the other terminalconnected to a common ground line |04. Winding |00 of relay 94 issimilarly connected. Winfiing 98 of relay 92 and winding |02 of relay 94are serially connected between the proper output lead from cable 90 andthe grounded line |04.

Relay 92 is provided with contacts |05 which when closed complete acircuit from the grounded line |04 through winding 95 of relay 92, line|08, line resistor H0, contacts ||2 of clearing .relay |4 and thence toa local source of power l l0. Relay 94 is equipped with a similar pairof contacts ||8, which when closed complete a path from grounded line|04 through winding |00 of relay 04, line |20, resistor |22, contacts||2 of relay H4 and thence to the source of operating power H0. Thecircuits just described cause the respective relays to lock in closedposition when actuated. Resistor Hi) is chosen so as to supply theproper operating current for locking up one of the converter relays suchas relay 92 and resistor |22 is chosen to supply the proper operatingcurrent to lock up one of the converter relays such as relay 94. Theserelays will require diieren't currents due to the multiple windings andthe possibility that a pair may be actuated together.

The converter relays are equipped with additional contacts whichcomplete circuits between a common line |24 and one or more of lines|25, l, |30, |32 or |34. For example, relay 92 carries contacts |36which complete a circuit between common line |24 and line |26, whilerelay 94 carries contacts |53 and |40 which complete circuits betweencommon line |24 and lines |20 and |30. The actuation of relays 92 and 54will therefore close circuits between common line |24 and lines |26, |28and |30. Similar contacts on the remaining converter relays willcomplete various combinations and permutations of connections betweenthe common line |24 and the lines |25, |23, |30, |32 and |34.

A source of transmission power |42 is connected to common line |24through line resistor |44, thence through the aforementioned permutationcontacts to lines |20, |23, |30, |32 and |34 which in turn are connectedto the commutator segments |45, |48, |50, |52 and |54, respectively,carried by the outer commutator ring of the distributor faceplate |56.It will be noted that the inner and outer commutator rings of thedistributor faceplate |55 carry certain notations in parentheses. Thesenotations have been added to simplify the understanding of the operationof the invention. The outer segmented ring corresponds with the standardcommutator used for transmitting 5 unit signals. The notations (l), (2),(3), (4), and (5 )indicate the elements or" the signals while (Start)and (Stop) indicate the transmitted operating functions. The localoperating functions are supplied to the apparatus through the innercommutator ring and are marked (Operate), (PP), (Select), (NN), and (CO)to correspond, as will appear, to the functions performed. Transmissionpower |42 iS also connected to a commutator segment |58 on the outercommutator ring of the distributor faceplate i56. A further commutatorsegment |60 is provided in the outer commutator ring of the distributorfaceplate 555 to which no connections are made. As is well known in theart suitable brushes are provided to sweep the aforementioned commutatorsegments and conduct any power appearing thereon to the transmissionring |62 and thence to the output circuits.

The circuit connections for causing the proper circuits to be set upindicating whether the next character to be transmitted is a letter or agure may best be understood from a consideration of Fig. 4, where letterrelays |54 and |66 and figure relays |59 and |70 are provided. One sideof the serially connected lwindings |72 and |14 of relays |58 and |20,respectively, is connected to ground line |24, the other side connectedto line |16. Similarly, the serially connected Windings |18 and |80 ofrelays |84 and |66, respectively, have one side connected to thegrounded line |04 and the other to line |82. Relays |64,

winding. 206 of relay LL and one of a pair of normally open contacts 264actuated by relay Relay FF is equipped withnormally open contacts;208which when closed complete a circuit from ground to lock up winding 2|Dof relay FF, thence to normally closed contacts 2|2 of relay LL,lineresistor 2|4 and a local source of powerf 2|6. Relay FF is alsoequipped with a tongue i 2|8 coacting with the normally open uppercontacts-220 and a normally closed lower contact 222. To the tongue 2li;is connected the normally open contact 225i of error relay 86 and,.throughcable 99, an output circuit from the `pileups 88 of thetranslator. The normally open contact 220 is connected to a pair ofnormally open contacts 226 of relay TTS and, through cable 96, to theoutput circuit from the pileups 88 corresponding to the letter G.

Relay EE is equipped with a pair of normally open contacts 239 which,when actuated, complete a circuit from ground through the lock-upwinding 232 of relay EE, the normally closed contacts 234 of relay NN,line resistor 236 and a local source of power 238. Relay EE is alsoequipped with a pair of normally open contacts 246which, when actuated,complete circuits between the upper of the normally open contacts 226 ofrelay TTS and the upper of normally open contacts 264 of relay NN,contacts v242 of error relay-84 and, through line resistor 244,commutator segment 246 of distributor faceplate |56, Relay EE is furtherequipped with normally closed contacts 248 which complete circuits fromthe open end of the differentially connected relay winding 258 of relayTTS, through the normally closed portion of make-before-break contacts252, to the other end of differential winding 256 of -relay TTS and alsoto commutator segment 254 of distributor faceplate |56. The center ofdifferentially connected relay winding 250 is connected to tapetransmitter 14 through line 16.

The normally open contact of make-beforebreak contacts 252 of relay TTSis connected to .a local source of power 256 through resistor 258.

Relay TTS is also equipped with a pair of normally open contacts 260which, when actuated, complete a circuit from the normally open contactof the make-beforefbreak contacts 262 of relay'NN, through line resistor264 to a local source of power 266. In addition, relay TTS is equippedwith a pair of normally open contacts 268 which, when actuated, completea circuit from ground to the inner and outer terminals, respectively, ofone of a pair of windings 210 and 212 of relay PP. The inner terminal ofwinding 212 of relay PP is connected through line resistor 216 tocommutator segment 218 of distributor faceplate |56. The outer terminalof winding 210, is connected to the normally open contacts 288 of relayPP which, when actuated, complete a path through line resistor 282 to alocal source of power 284. Relay PP is also equipped with a pair ofnormally open contacts 285 which, when actuated, complete a circuitbetween the normally closed contact of make-before-break contacts 252 ofrelay NN and commutator segment 2880i distributor faceplate |56.

Relay NN is actuatedbycurrent flow through winding 296, one end .of.which is connected to ground and the other to `the make-before-breakcontacts 262 of the relay NN.

Commutator segment 292 of distributor faceplate |56 is connected throughline resistor 294 to the winding of clearing relay H4, the other end ofwhich is connected to ground.

Commutator segments? 246, 254, 218, 288 and 292 are sequentiallysupplied with positive power from local source 296 through line resistor298 as they are swept by a suitable brush connecting them and slip ring300.

Suitable resistor-condenser networks may be utilized throughout thecircuit to minimize arcing at the relay contacts. Several of suchnetworks has been illustrated. The operation of the invention will bedescribed with reference to Figures 3, 4, 5 and 6.

Referring to Fig. 3, it will be assumed that the tape transmitter 22 hasbeenset up to transmit a code signal consisting of 2 space elements, 2mark elements, a space element, a mark element and a space elementcorresponding to the letter R. The current will be fed from a localsource of power 68 through translator relays 46, 38 and 34,respectively, causing corresponding translator pileups 88 to be actuatedand set up an output path to lead to the cable 90 corresponding to theletter R. Similarly, if any other code combination consisting of Smarkelements and 4 space elements were set up by the tape transmitter 22corresponding paths would be established by the translator relaysandtheir corresponding pileups and one of the output paths to the cable9U completed.

In order to insure the efficient operation ci the translator pileups 88it may be desirable to include on the relays having the greater numberof contacts additional actuating windings. Such windings are representedin Fig. 3 by coils 362 and 365. It will be noted that these coils areelectively in parallel with the relay coils 32 and 38; coil 362 havingone end connected to ground the other fed through cable 98 to a pair ofcontacts 386 actuated by relay 32 and thence through Eine resisto-r 368to a positive source of supply 68, and coil 34 having one side Connectedto ground and the other fed through cable 96 lto contacts 35! actuatedby relay 34 and thence to line resistor 3I2 and the local source ofpower 56. Although only two of such windings are shown, it will .beobvious that desired number may be used.

Referring to Fig. 4, it will be seen that the cable Q6 supplies theoutputs of the translator to a plurality of converter relays, six ofwhich are shown. Continuing the example chosen of the letter R beingtranslated, it will be seen that corresponding lead from the cable 90passes through one winding 3|4 of converter relay H6 and thence tegrounded lineV |64. Upon the reception of an operating impulse converterrelay l1!) will be actuated and its contacts closed. The closure ofcontacts SEE will complete a path from the grounded line |64 throughrelay winding 3|4 to line itil which, as will be seen from Fig. 5, willcomplete a through line resistor contacts H2 ci relay H4 to a localsource of power H6 causing relay |16 to be locked in closed position.Closure of contacts 3|8 and 326 of relay 16 will complete paths fromcommon line i524 to line-s |28 and |32, respectively.

Similarly, if a code combination corresponding to the letter B had beenset up through the transmitter the corresponding lead from the cable 98Would have energized relay |68 which would have then been locked inclosed position and its remaining contacts complete paths from commonline |24 to lines |26, |32 and |34. Any other code combination whichwould set up paths through one Winding of any of the converter relayswould set up corresponding permutations of connections between thecommon line |24 and lines |26, |28, |38, |32 and |34.

It Will be noted that the converter relays are arranged in pairs. Bymeans of this arrangement it is possible to accomplish the conversion ofsignals with a fewer number of relays. For instance, converter relay 92sets up a circuit be-` tween common line |24 and line |26 whileconverter relayed sets up circuits between common line |24 and lines |28and |38. Assuming that the lead corresponding to the letter U has beenset up through the translator coil 88 on relay 8?. and the seriallyconnected coil |82 on relay 84 will both be energized completingcircuits cetween grounded line 24 and lines 128, |28 and |38.Accordingly, these two relays can set up three different codecombinations. The remaining converter relays are similarly connected inpairs.

Referring now to Figs. and 6, it will be seen that common line |26 leadsto a local source of power |42 through resistor |44 and that the lines|26, |28, |38, |32 and |34 leadto cornrnutator segments |46, |48, |58,|52 and |54 of the distributor faceplate |56. Accordingly, whenconverter re lay |18 is actuated power from the local source |42 will hefed to commutator segments |48 and |52 and when the cuter distributorring is swept by the brushes there will be fed to the output impulsescorresponding'to the nre unit code for the letter RJ The operation ofthe other converter relays will set up similar paths to the outerdistributor ring of the distributor faceplate |56 and correspondingsignals fed through the brushes to the output.

The operation of the error insertion Will be described with particularreference to Figs. 3 and 6. The transmission from the tape transmitter22 of a signal containing less than 3 mark elements will, through theaction of currents flowingr through only one or tWo of the correspondingparallel impedance devices 44, 46, 48, 58, 52, 54 and l2, actuate errorrelay 64. Error relays 82 being adjusted to operate only on currentsflowing through three or more of the parallel impedance devices will notbe actuated. Accordingly, a path will be set up from the operate segment246 of the distributor faceplate |56 through contacts 242 of error relay84, thence through the lower contact of error relay 82 to the tongue 2i8 of relay FF. Similarly, if a signal containing more than 3 markelements is fed from the tape transmitter 22, error relays 88, 82 and 84will be actuated and a path set up from the operate segment 246 ofdistributor faceplate |56 through contacts 242 of relay 85, the uppercontacts of relay 82, the upper contacts of relay 88 and thence to thetongue 2|8 of relay FF. It will thusbe seen that a path can heestablished to the pileups ups which are not under the control of eachtranslator relay and also make possible the elimination of one of thetranslator relays.

In converting from a seven unit code to a five unit code there arecertain combinations of the mark and space elements of the seven unitcode containing the predetermined num-ber of mark elements which are notrepresentative of intelligence. .Such a combination is represented by asignal in which the third, fth and seventh elements are mark elementsand the remaining elements spaces. It will be seen that Ibecause of thefact that the normal number of mark elements are present a path would beestablished through the error detector relays 88, 82 and 84 to thepileups 88 of the translator.

In order that these combinations may -be recognized as transmitted inerror, these combinations are fed through the cable 88 directly to thetongue 2|8 of relay FF. Similarly, where a code combination is used inthe seven unit code indicative of an error, the corresponding outputcircuit through the pileups 88 of the translator are fed through cable88 directly to the tongue 2|8 of relay FF.

The method of inserting an error indication in the converter circuitwill be described in connection with Figs. 3, 4 and 6. The Figure"circuit connects to the converter relay |68 through one Winding |82 ofrelay FF so that whenever a ligure selection occurs relay FF is actuatedand is locked up through a circuit from ground through winding 2|8, itsown contacts 28S, the normally closed contacts 2|2 of relay LL, lineresistor 2|4 to a sour-ce of local power EIB. The Letter circuit isconnected .to converter relay |64 through the winding 288 to relay LL.Therefore, whenever -a letter selection occurs relay LL will operate andthe opening of s contacts 2|2 will release relay The function of relaysFF and LL is, therefore, to register the last case shift selectionpassed through the sysures the operate impulse may :be traced throughthe tongue 2|8 of relay FF 'to contact 228 of relay FF and thencethrough cable 9U to the G winding 322 of converter relay |68. Thisarrangement automatically converts the error selection to an upper caseG indicative of an error.

If the last case shift transmission preceding an error be Letten theoperate impulse is routed through tongue 2|8 of relay FF, contact 222 ofrelay F'F and winding |86 of relay EE to the windings |l2 and |74 ofconverter relays |68 and |18, respectively, causing a gure codecombination to be transmitted over the signalling circuit. From thispoint on the sequence of operation is as follows: Relay EE is actuatedand locked up through a circuit from ground through winding 232,contacts 238 of relay EE, contacts 234 of relay NN, line resistor 236and a local sour-ce of power 238. The windings of relay TTS beingdifferentially connected are eiectively in series with a circuitbeginning with the impulse received from commutator segment 254 ofdistributor faceplate |56 and extending through the windings of the tapeadvancing solenoid 14 of the tape transmitter 22 to ground. The normalfunction of this circuit is to electromechanically operate tapetransmitter 22 and advance the perfoi'ator tape. However, when onewinding of relay TTS is opened bythe operation of relay EEin' responseto an error signal the neXt Succeeding select impulse from commutatorsegment 254 of distributor faceplate |56 causes relay TTS tooperate andlock up through a circuit completedthrough its make-before-breakcontacts 252`- from a source of -POWSI 255 through une resistor258-,contacts 252, one portion of the winding'- 25|)v of' relay TIS,tape operating solenoid 14ifof tape transmitter 22 to ground. Theoperatio'rrof relay TTS establishes a circuit from the operate impulsethrough a pair lof contacts '240 of *relay EE, contacts 226 of relay'I'TS to the G lead in cable 98'. The lead from cable 9D is fed throughcoil 322 of converter relay |56 establishing a G combination.

Contacts 2168 on relay TTS complete a circuit from" commute-tor segment218 of 4distributor faceplate |56 rthrough resistor 215, winding 212 of"relay 214 and thence to ground. Relay PP will be locked into positionby means of a curren-t ilow through a circuit from a local source of*power 284, line resistor 282, contacts 28D' of relay PP, winding 210 ofrelay PP, contacts 2168 of `relay"I"ISto ground.

Relay PP will operate on the impulse from com-mutator segment 218 duringthe G transmission 'and completes the operating circuit fromcommutatorsegment 288, contacts 286 of relay PP through the closedportion of make-beforebreak contacts 262 lof relay NN, the Winding ofrelay NN -to ground. Relay NN will be locked into position by means of acircuit completed fromvground through the winding of relay NN, thenormally open contact of the make-beforebreak contacts 252 of relay NN,contacts 250 of relay TTS, line resistor 2'54 and the local source ofpower 266. Contacts 204 on relay NN connect the'operate impulse to line|82 which feeds the operating impulse to the windings |18 and |80 ofconverter relays |154 and |88, respectively, es-

tablishing a Letter combination. The operation of relay NN openscontacts 236 of relay NN which releases the locking circuit of relay EEand prepares relay TTS to release in response to the next select impulsefrom commutator segment 254 of distributor faceplate |56 which occursduring the letters transmission. This release occurs since the openingof contacts 248 0f relay EE again connects the windings of relay TTSdifferentially.

When the brush between the ring 360 and the inner commutator ofdistributor faceplate |56 connects the local source of power 296 tocommutator segment 292 of distributor |56 a circuit is completed throughline resistor 294 to the winding of clearing relay H4 and thence toground. The actuation of clearing relay ||4 opens contacts l2 restoringthe converter relays to their normal unoperated position.

Cam 3D is positioned on the brush shaft and is phased so as to open thecircuit for operating the tape transmitter 22 during the time whenselections are being established.

Having thus described our invention, what We claim is:

l. In a telegraph system utilizing uniform length code signals having axed number of mark and space elements, a plurality of parallel impedancedevices eachx respectively actuated by said niark elements, a pluralityof errordetecting relays actuated under control of currents flowingthrough said impedance circuits,

10 translating means responsive to the mark ele` ments of said codesignals and having a shift device adapted tc actuate a plurality ofshift conditions in the translating means each in response'v to acorresponding plurality ci code signals, eachl by said error-detectingrelays for causing said converter means to set up a predetermined codegroup indicative of an error whenever said signals contain an abnormalnumber of marking4 said shift device to select elements and actuatin oneof said shift conditions during an error indi'- cation and to returnsaid shift condition to its' preceding condition.

2'." In a telegraph system utilizing uniform length code signals haringa fixed number of mark and space elements, a plurality'of parallel"impedance devices each respectively actuated by said mark elements, aplurality of error-detecting'l relays actuated under control of currentsflowing" through said impedance circuits, translating' means comprisinga plurality of switching cir-'- cuits actuated by said mark elements anda shift circuit to select one of a plurality of selected shift`conditions in response to a selected code signal corresponding theretoand to maintain said shift condition until a succeeding one of saidselected signals is received, means actuated by said translating meansfor converting said signals into codeY signals having a different numberof mark and space elements, and means actuated by said errordetectingrelays for causing said' converter means to set up a predetermined codegroup indicative of an error whenever said signals contain an abnormalnumber of marking elements and fol" causing the selection of apredetermined shift condition.

3. In a telegraph system utilizing uniformlength code signals having afixed number of mark and space elements, a plurality of parallelimpedance devices each respectively actuated by said mark elements, aplurality of error-detecting relays actuated under control of currentsflowing through said impedance circuits, translating mean-s responsiveto the mark elements of said code signals and a shift circuit to selecta selected one of two shift conditions in response to a selected codesignal corresponding thereto and to maintain said shift condition untila succeeding one of said selective signals is received, a plurality ofswitching means actuated by certain circuits within said translatingmeans arranged to convert said signals into code signals having adifferent number of mark and space elements, and means actuated by saiderror-detecting relays for causing said converter means to set up apredetermined code group indicative of an error whenever said signalscontain an abnormal number of marking elements and for causing theselection of a predetermined shift condition.

4. In a telegraph system utilizing uniform length code signals having afixed number of mark and space elements, a plurality of parallelimpedance devices each respectively actuated by said mark elements, aplurality of error-detecting relays actuated under control of currentsowing through said impedance circuits, translating means comprising apluirality of switching circuits actuated by said mark elements and ashift 4circuit to select one of a plurality of selected shift conditionsin response to a selected code signal corresponding thereto and tomaintain said shift condition until a succeeding one of said selectedsignals is received, a plurality of switching means actuated by saidtranslating means arranged to convert said signals into code signalshaving a different number of mark and space elements,4 :means forcausing certain of said translator switching circuits to actuate aplurality of said converter switching means, means actuated by saiderror-detecting relays for causing said converter means to set up apredetermined code group indicative of an error whenever said signalscontain an abnormal number of marking elements, means for causing saidconverting means to set up said error indicative code group when saidsignals contain a normal number of mark elements in predetermined spacerelationship, and means for causing the selection of a predeterminedshift condition during an error indication and the return to the lastpreceding shift condition thereafter.

5. In apparatus for changing seven element into live element codesignals, a. plurality of paralle] impedance devices each respectivelyunder the control of one of the elements of said seven unit code, aplurality of error detecting relays actuated under the control ofcurrents flowing through said impedance circuits, a plurality oftranslator relays, one for each velement of said seven unit code,provided with multiple resting and operating contacts arranged tocomplete one only of a number of output paths, a second set of relaysarranged to be actuated through said output paths provided with multiplecontacts arranged to complete paths corresponding to said five elementcode, means actuated by said error detecting relays for causing saidsecond set of relays to set up a ve element code group indicative of anerror Whenever said seven unit signals contain an abnormal number ofmarking elements, means to actuate a shift mechanism in a chosen one ofa plurality of conditions in respon'se to a corresponding set of codesignals and to maintain said shift condition until another 12 dilferentone of said plurality of corresponding code signals is received, andmeans to maintain a predetermined shift condition in response to eachsaid error signal and to return to the preceding shift condition beforereception of the next signal shift.

6. In a telegraph system utilizing uniform length code signals havingseven mark and space element-s, a plurality of parallel impedancedevices each respectively actuated by said mark elements, a plurality oferror-detecting relays actuated under control of currents flowingthrough said impedance circuits, translating means responsive to themark elements of said code signals and having two shift conditions eachassumed in response to a predetermined code signal, each said conditionbeing maintained until the reception of the other code signal operativeto return said translating means to the other said shift condition,means actuated by said translating means for converting said signalsinto code signals having five mark and space elements, and meansactuated by said errordetecting relays for causing said converter meansto set up a predetermined code group indicative of an error Wheneversaid signals contain an abnormal number of marking elements and to causethe selection of one of said shift conditions during an error indicationand on reception of the next non-erroneous signal thereafter to returnto the preexisting shift condition.

JAMES A. SPENCER.

LEWIS A. THOMAS.

REFERENCES CITED rlhe following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,152,772 Potts Apr. 4, 19392,153,737 Spencer Apr. 11, 1939 2,309,222 Spencer Jan. 26, 19432,370,989 Nicols Mar, 6, 1945

